Double balanced mixers in the radio frequency arts generally, and double balanced mixers in ring diode configurations including four or eight diodes are well known. See for example the publication RF Signal Processing Components by Watkins-Johnson of Palo Alto, Calf. Such mixers can be employed for mixing signals, conducting bi-phase modulation and performing phase detection operations.
A problem that arises in the construction of such circuits is that the diodes employed display considerable variation in characteristics. In other words, the diodes in the ring are not all alike electrically, which considerably degrades the performance of the entire ring. The degradation frequently involves the production of spurious modulation products that compromise the intended function of the mixer circuit. These products must then be removed by additional circuit elements such as filters.
Accordingly, it is an object of this invention to compensate for the effect of dissimilar diodes in the ring of a double balanced mixer circuit.
Additionally, it is an object of the invention to compensate for the adverse effects of dissimilar didoes in the ring of the double balanced mixer by injecting DC currents symmetrically into the diode ring.
Furthermore, it is an object of the invention to develop an eight-diode ring double balanced mixer circuit including four symmetrical RF ports interspersed or interleaved with DC bias injection ports for diode dissimilarity compensation.
It is an additional object of the invention to establish a DC bias injection eight diode ring double balanced mixer circuit for RF application.
It is a further object of the invention to develop an eight diode element ring double balanced mixer circuit including eight terminals for connecting the diode elements in ring configuration and additionally thereby establishing two pairs of RF ports and two pairs of DC injection ports.
It is additionally an object of the invention to establish an eight diode ring double balanced mixer with symmetrically disposed, interleaved, interspersed, and cooperative pairs of RF and DC injection ports.
It is a further object of the invention to provide a ring diode double balanced mixer with pairs of DC bias injection conjugate ports effective for providing cooperative positive and negative DC injection of electric current.
It is furthermore an object of the invention to reduce or suppress spurious and/or odd order modulation products from a ring diode double balanced mixer comprising inadvertently dissimilar diode elements by injecting DC currents at symmetrical injection terminals distributed about the diode ring.